In an electric resistance welded pipe manufacturing line, a band shape material called a skelp is gradually formed into a cylindrical shape, and continuously welded and jointed by heating a butt edge portion and pressing the heated butt edge portion with squeeze rolls, so that an electric resistance welded pipe with a circular section serving as a product is continuously manufactured. In such an electric resistance welded pipe manufacturing line, various types of products having different sizes are commonly manufactured, and for this, roll replacement for changing size of forming rolls is frequently performed.
Regarding this roll replacement, it is unexceptional also in a squeeze roll stand installed at a joint position of the electric resistance welded pipe manufacturing line, and squeeze rolls are replaced in accordance with size of a product to be manufactured. A method thereof is as follows. As the squeeze rolls in the squeeze roll stand, there are provided a lower roll for supporting an open pipe coming in with a facing edge portion facing upward from the lower side, a pair of left and right side rolls for pressing the open pipe from both sides, and a pair of left and right upper rolls for pressing a vicinity part of the facing edge portion from the obliquely upper side. In the roll replacement, all these rolls are replaced with rolls corresponding to size of a new product. However, at the time of replacing the lower roll and the left and right side rolls, the upper rolls get in the way. Therefore, in the roll replacement of the squeeze rolls, there is a need for detaching the upper rolls before replacement of the lower roll and the left and right side rolls.
However, detachment of the upper rolls is conventionally performed by suspending an upper roll assembly by a crane and separating the upper roll assembly from a stand main body on the lower side. The upper roll assembly separated from the stand main body is conveyed to off-line. After replacement of the upper rolls is performed here, the entire upper roll assembly is returned in place. While the upper roll assembly is detached, the replacement of the side rolls and the lower roll in the stand main body is performed.
Since a roll replacement work in the squeeze roll stand is extensive and troublesome as described above, various improvement measures are proposed in Patent Documents 1 to 3. However, since the measures are basically separation by a suspending work of the upper roll assembly, such a great effect as to expect is not obtained in a current situation. That is, in a case of the separation by the suspending work of the upper roll assembly, the work itself is extensive and troublesome. Besides, there are many problems such as a need for a lot of time for detaching wires and pipes connected to the upper roll assembly from an exterior at each time of the work and for resuming after the work. Thus, productivity is remarkably lowered.
Regarding a material made to be a pipe after finishing welding in the squeeze roll stand, an outer surface welding bead is generally removed by a bead grinding device continuously provided on the downstream side of the squeeze roll stand (refer to Patent Documents 4 to 7). That is, the squeeze roll stand is commonly combined with the bead grinding device on the line downstream side. In the bead grinding device, height of a grinding blade supported on the line is adjusted in accordance with product size. A height adjustment mechanism is also provided on the line together with the grinding blade.